this is a line spoken by Frank Morgan's depiction of the Wizard of Oz in the 1939 film, which debuted 20 years after Baum's death. It did not actually appear in the "Wonderful Wizard of Oz". The ending of "Steam Engines of Oz" wrongly attributes this phrase to Baum when it would've originated from the 1939 adaptation script writers Langley/Ryerson/Woolf.
More quotes by L. Frank Baum
Some of my youthful readers are developing wonderful imaginations. This pleases me.
I think the world is like a great mirror, and reflects our lives just as we ourselves look upon it.
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Love looks not with the eyes, but with the mind,
And therefore is wing'd Cupid painted blind.
To fear love is to fear life, and those who fear life are already three parts dead.
Not for the body, but for the heart; companion and company are needed.
Love seldom haunts the breast where learning lies,
And Venus sets ere Mercury can rise.
Attribution
Quote text and notes from Wikiquote: L. Frank Baum (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.